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Merge olga.mysql.com:/home/igor/mysql-4.1-opt

Browse source 
into  olga.mysql.com:/home/igor/mysql-5.0-opt


sql/item_subselect.cc:
  Auto merged
mysql-test/r/subselect.result:
  Manual merge
mysql-test/t/subselect.test:
  Manual merge
sql/item_subselect.h:
  Manual merge
This commit is contained in:
unknown 2006-12-12 11:53:09 -08:00
commit 22192d083a
4 changed files with 44 additions and 3 deletions
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19
sql/item_subselect.cc
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@ -349,6 +349,7 @@ Item_singlerow_subselect::select_transformer(JOIN *join)
*/
!(select_lex->item_list.head()->type() == FIELD_ITEM ||
select_lex->item_list.head()->type() == REF_ITEM) &&
!join->conds && !join->having &&
/*
switch off this optimization for prepare statement,
because we do not rollback this changes
@ -373,8 +374,6 @@ Item_singlerow_subselect::select_transformer(JOIN *join)
*/
substitution->walk(&Item::remove_dependence_processor,
(byte *) select_lex->outer_select());
/* SELECT without FROM clause can't have WHERE or HAVING clause */
DBUG_ASSERT(join->conds == 0 && join->having == 0);
return RES_REDUCE;
}
return RES_OK;
@ -2277,6 +2276,22 @@ bool subselect_single_select_engine::no_tables()
}
/*
Check statically whether the subquery can return NULL
SINOPSYS
subselect_single_select_engine::may_be_null()
RETURN
FALSE can guarantee that the subquery never return NULL
TRUE otherwise
*/
bool subselect_single_select_engine::may_be_null()
{
return ((no_tables() && !join->conds && !join->having) ? maybe_null : 1);
}
/*
Report about presence of tables in subquery